SHEAR STRENGTH ASSESSMENT OF REINFORCED CONCRETE COLUMNS

Seismic assessment of reinforced concrete structures depends on strength values that can be estimated with sufficient accuracy only when the modes of failure are ductile.The level of accuracy degrades when considering brittle mechanisms of resistance, particularly when focusing on shear transfer and the associated deformation capacity.In this paper, it has been found that an important factor affecting the primary estimation of the shear strength is the inclination of the plane of sliding failure , identified as 45 o by the Mörsch truss, an assumption that does not comply with experimental results on columns.Using basic mechanics, the proposed model improves the correlation of the estimations, regarding both the concrete and transverse reinforcement contributions, V c and V s , presenting a new method for estimating , in particular in cases where applicability of the MCFT is limited by sparse stirrup spacing (i.e., assumptions about smearing of reinforcement are inappropriate).The concrete contribution component is established from first principles having as point of departure the fact that concrete directly supports shear only over the compression zone of the member, where cracks may be assumed to have closed.Conditions of concrete diagonal tension cracking and compressive crushing are both considered.Published experiments are used to guide and verify the development of the analytical model.